Cold Keystone

 is an item in Tyranny.

Description
This fist-sized stone, unusually cold to the touch, bears an ancient sigil of unknown meaning. Stones like this are not uncommon in the Oldwalls, and often fit as keystones into larger structures.

Use

 * A Breach Between Worlds: Found at Blade Grave Oldwalls - Central, at the end of the right-hand upstairs corridor. Activate the beacon next door with a red torchkey and use the wall switch to open the room.